To determine the behavior of \(\bar{\psi }\Gamma \psi \) , with \(\Gamma \)  being one
of the terms in (REF ), under combined parity reflection \(\mathcal {P}\)  and time
reversal \(\mathcal {T}\) , recall the usual definition of these transformations in \(3+1\)  dimensions [1]}:
\(\mathcal {P}:&\, \psi (t, \mathbf {x}) \rightarrow \mathcal {P}\psi (t, \mathbf {x}) \mathcal {P}^{-1} &&=\gamma ^0 \psi (t, -\mathbf {x}),\\\mathcal {T}:&\, \psi (t, \mathbf {x}) \rightarrow \mathcal {T}\psi (t, \mathbf {x}) \mathcal {T}^{-1} &&=i \gamma ^1 \gamma ^3 \psi ^*(-t, \mathbf {x}).\) 
